> All of these things are extremely cost sensitive. Say their profit margin is 1%. If you offer to pay them a 1% higher price, you're offering to nearly double

> All of these things are extremely cost sensitive. Say their profit margin is 1%. If you offer to pay them a 1% higher price, you're offering to nearly double their profits on whatever they sell to you. Admittedly, that only works if you are a sufficiently large portion of their business. If you're a tiny percentage, then it may take a lot more to motivate them if their other customers aren't willing to pay more.